The present invention relates generally to manufacturing processes and, more particularly, to a manufacturing process that uses statistics to establish optimal limits for the critical characteristics of manufactured products.
The process of manufacturing a product presents many challenges to bringing the product to market for the least cost, while maintaining product quality. Manufacturing quality products for the least possible cost is a universal objective in all industries. In order to produce high quality products while maintaining low production costs, it is necessary for the manufacturer to continually assess product quality and process capability.
Many industrial concerns use statistics as a means to improve the quality and the efficiency of their manufacturing processes. The two most common ways of viewing quality are the "traditional approach," which views quality in terms of conformance to product specification and the "new approach," which views quality in terms of reduced variability around a target or nominal critical characteristic. These approaches assume that quality is measured by the variation of critical characteristics from a target or nominal value. However, these approaches are flawed to the extent that they fail to consider the influence that market factors have on manufacturing costs and profitability. A continuous pursuit of excellence or perfection, without regard to customer needs, the expense of achieving quality beyond what the relevant market demands, or the quality and price of the competitors' products is characteristic of both the "traditional" approach and the "new" approach. As a result these two approaches generally lead to the manufacture of products that exceed the needs of the customer and exceed the cost many customers are willing to pay.
The present invention differs from the approaches to quality well known in the art, which use upper and lower control limits to determine whether critical characteristics of a manufactured product are outside of a rule of order, signifying that a process is out of control or unable to consistently perform within a particularly degree of variability. The present invention is unique in that its purpose is to define an operating range to be used to identify acceptable product offered for sale to customers in the relevant market and to identify non-conforming, unacceptable product, which is rejected and considered unusable. Furthermore, the methods well known in the art endeavor to minimize the variance of manufactured products critical characteristics from a target or nominal value. However, the present invention is based upon the premise that there is no added value in minimizing the variance of the critical characteristics from the nominal or target value, provided the critical characteristics are within the established operating range. An objective of the present invention is to establish an operating range that is bound by the points of diminishing returns for the critical characteristics of the manufactured product.
It would be advantageous to provide a means for manufacturing a product whose quality does not exceed the customer's needs and whose price does not exceed that which the customer is willing to pay. Accordingly, another objective of this invention is to provide a means for manufacturing products whose critical characteristics are such that the quality demands of the customers in the relevant job are met, while production costs are minimized. Moreover, an additional objective of this invention is to provide a manufacturing process for establishing optimal operating limits for the critical characteristics of manufactured products.